Search

The synthesis of hexa- and octahydrobenzothiopyran-4-one S,S-dioxides 1–4 is described. The regioselective and stereospecific H/D-exchange of the hydrogens α to the SO2 group is accomplished by careful control of reaction conditions. The comparison of the PMR spectra of the deuterio and protio derivatives allows the establishment of the mode of ring fusion.

The cyclic sulfones 1 , 2 , and 3 are lithiated in benzene with n-butyllithium. Lithiation is demonstrated to lead to α-mono, α,α′-di and/or α,α-di and α,α,α′ trimetallation. The lithiated sulfones are chlorinated with hexachloroethane (HCE). Some mechanistic aspects of the reaction of the lithiosulfones with vicinal dihalides are discussed.

The cis fused bicyclic sulfones 1a, 1c and 3a are lithiated in benzene with n-butyllithium under concomitant cis/trans isomerization of the ring fusion, involving intramolecular proton transfer. H/D exchange of the three α-hydrogens in protic solvents proceeds with retention of configuration. The lithiated sulfones are chlorinated with hexachloroethane (HCE) and show a strong preference for introduction of halogen at an equatorial α-position.

The KOtBu-induced Ramberg-Backlund reaction of the trans bicyclic halosulfones 1 and 2 is studied in DME and DMSO. Strong indications are obtained that the reaction proceeds via the intermediate Z-episulfone with retention-inversion (involving exo-S-geometry). 1 Base induced epimerization at the nucleofugal centre (from axial to equatorial halogen) is demonstrated in DMSO.